Mobile communications device users are increasing dependent on the ability to use their mobile communications devices all over the world. Mobile users who travel out of their “home network” are called roamers. There are many different mobile communications network operators throughout the world, each having its own territories, technical systems, and business systems. Currently, roamers are typically not able to travel freely and have a seamless experience in any operator's network. There are currently disadvantages for both the roaming user and the network operator.
For example, roamers who roam frequently between two countries often have a need for a local phone number in each network; either to enable local users to call them at a cheap rate without worrying about international direct dial (IDD) calls, or to present a multi-national appearance. Such roamers typically buy a local pre-paid subscription from the local network operator and use the local phone number to make outgoing calls. However, if the roamer has a single phone and has swapped out the HPMN SIM card, the roamer will not be able to receive HPMN calls and SMS messages. Also, when the roamer is back in his HPMN, he may not be able to receive calls on their FPMN number. Such roamers must also change the SIM in their mobile handset each time they roam in the local network, which is not convenient. The home network operator is also disadvantaged because the home network operator is not receiving the roaming revenue. It is thus desirable to facilitate roaming, even international roaming with minimum effort on the part of the roaming user, such as eliminating the requirement for different SIMs.
Mobile communications network operators face tremendous challenges in growing their revenue streams in the face of increasing competition and pricing pressures. Roamers are an attractive source of revenue for operators sometimes constituting as much as 8% to 40% of an operator's total revenue. It is thus desirable to be able to influence or control the roamer's network choices in order to maximize the benefits to the operator and to the subscriber user.
Acronyms
Following are a list of acronyms used herein.    APMN: Associated Public Mobile Network for SMS Inter-working;    AuC: Authentication Center;    BCSM: Basic Call State Model;    CALEA: Communications Assistance for Law Enforcement Act;    CAMEL: Customized Applications for Mobile network Enhanced Logic;    CAP: CAMEL Application Part;    CDMA: Code Division Multiple Access;    CdPA: Called Party Address;    CDR: Call Detail Record;    CFB: Call Forwarding in Busy;    CFNRc: Call Forwarding on Not Reachable;    CFNRy: Call Forwarding on No Reply;    CFU: Call Forwarding Unconditional;    CgPA: Calling Party Address;    CSD: Circuit Switch Data;    CSI: CAMEL Subscription Information;    DB: Database;    D-CSI: Dialled Services CAMEL Subscription Information;    DDF: Digital Distribution Frame;    DP: Detection Point;    DPC: Destination Point Code;    DTN: Deflected To Number;    E1: Wide Area Digital Transmission Scheme used predominantly in Europe;    ECF: Event Charging Function;    EDP: Event Detection Point;    FPMN: Foreign Public Mobile Network who intends to partner with HPMN for Multiple MSISDN Service;    FTN: Forwarded-To-Number typically used in Call Forwarding;    FTP: File Transfer Profile or File Transfer Protocol;    FSMS: Fixed Line SMS;    Ga: Charging data collection interface between a CDR transmitting unit and a CDR receiving functionality;    Gb: Interface between an SGSN and a BSS;    Gc: Interface between a GGSN and an HLR;    Gd: Interface between an SMS-GMSC and an SGSN, and between an SMS-IWMSC and an SGSN;    Gf: Interface between an SGSN and an EIR;    GGSN: Gateway GPRS Service Node;    Gi: Reference point between GPRS and a packet data network;    GMLC: Gateway MLC;    GMSC: Gateway MSC;    GMSC-H: GMSC in HPMN;    GMSC-F: GMSC in FPMN;    GMSC-V: GMSC in VPMN;    Gn: Interface between two GSNs within the same PLMN;    Gp: Interface between two GSNs in different PLMNs;    GPRS: General Packet Radio Service;    GPRS-CSI: GPRS CAMEL Subscription Information;    gprsSSF: GPRS Service Switching Function;    Gr: Interface between an SGSN and an HLR;    GRX: GPRS Roaming Exchange;    Gs: Interface between an SGSN and an MSC/VLR;    GSM: Global System for Mobile Communications;    gsmSCF: GSM Service Control Function;    gsmSRF: GSM Specialised Resource Function;    gsmSSF: GSM Service Switching Function;    GT: Global Title (SS7 parlance);    GTT: Global Title Translation;    HLR: Home Location Register;    HPLMN: Home PLMN;    HPMN: Home Public Mobile Network who intends to provide MSISDN Service;    HSCSD: High Speed Circuit Switched Data;    ID: Identification;    IDD: International Direct Dial;    IDP: Initial DP;    IE: Information Element;    IF: Information Flow;    IMSI: International Mobile Subscriber Identity (of HPMN);    IMSI-H: HPMN IMSI;    IMSI-F: FPMN IMSI;    IN: Intelligent Network;    INAP: Intelligent Network Application Part;    IOSMS: Inter Operator SMS within HPMN;    IP: Intelligent Peripheral;    IPLMN: Interrogating PLMN;    IREG: International Roaming Expert Group;    ISC: IP Multimedia Subsystem Service Control Interface;    ISDN: Integrated Service Digital Network;    ISUP: ISDN User Part message from SS7 stack;    Iu: Interface between the RNS and the core network;    IVR: Interactive Voice Response;    kbit/s: Kilobits per second;    Ki: Authentication Key;    Kc: Ciphering Key;    LAN: Local Area Network;    LCF: Late Call Forwarding;    LCS: Location Services;    LMU: Location Measurement Unit;    LSA: Localised Service Area;    MAP: Message Application Part (from GSM 09.02 GSM Standards);    Mbit/s: Megabits per second (Mbit/s);    M-CSI: Mobility Management event Notification CAMEL Subscription Information;    MF: Mobile Forwarding;    MGT: Mobile Global Title (derived from IMSI);    MIMM: Multiple IMSI Multiple MSISDN Service;    MISM: Multiple IMSI Single MSISDN Service;    MLC: Mobile Location Center;    MMS: Multimedia Messaging Service;    MMSC: Multimedia Messaging Service Centre;    MO: Mobile Originating;    MSC: Mobile Switching Center;    MSISDN: Mobile Subscriber ISDN Number (phone number);    MSISDN-H: MSISDN of the Multiple MSISDN Service allocated by HPMN in HPMN numbering plan;    MSISDN-F: MSISDN of the Multiple MSISDN Service subscriber in the FPMN (Co-operating VPMN) numbering plan;    MSRN: Mobile Station Roaming Number;    MT: Mobile Terminated;    MTP: Message Transfer Part;    NA: North American;    N-CSI: Network CAMEL Service Information;    NNI: Network Node Interface;    OAM&P: Operations, Administration, Maintenance, and Provisioning;    O-BCSM: Originating Basic Call State Model;    OCN: Originally Called Number (same as ODN);    O-CSI: Originating CAMEL Subscription Information;    ODB: Operator Determined Barring;    ODN: Originally Dialed Number (same as OCN);    OM: Outreach Messaging;    OMAP: Operations, Maintenance, and Administration Part (SS7);    OR: Optimized Routing;    OSS: Operator Specific Service;    OTA: Over-the-Air;    PCI: Peripheral Component Interconnect;    PDA: Personal Digital Assistant;    PDP: Packet Data Protocol;    PIC: Point In Call;    PLMN: Public Land Mobile Network;    PMN: Public Mobile Network;    PRN: Provide Roaming Number MAP message;    PSL: Provider Subscriber Location;    R: Reference point between a non-ISDN compatible TE and MT;    RAID: Redundant Arrays of Inexpensive Disks;    SCP: Service Control Point;    SCCP: Signal Control Connection Part;    SG: Signal Gateway;    SGRF: Signal Gateway Relay Framework;    SGSN: Serving GPRS Service Node;    SIM: Subscriber Identity Module;    SIMM: Single IMSI Multiple MSISDN Service;    SLPI: Service Logic Program Instance;    SLR: Subscriber Location Report;    SM: Session Management;    SME: Short Message Entity;    SMF: Service Management Function;    SMLC: Serving MLC;    SMP: Service Management Point;    SMPP: Short Message Peer to Peer;    SMS: Short Message Service;    SMSC: Short Message Service Center;    SMSC-A: SMSC in APMN;    SMSC-F: SMSC in FPMN;    SMSC-H: SMSC in HPMN;    SMS-CSI: Short Message Service CAMEL Subscription Information;    SMTP: Simple Mail Transfer Protocol;    SNMP: Simple Network Management Protocol;    SPC: Signalling Point Code;    SRI: Send Routing Information MAP message;    SS: Supplementary Service;    SS7: Signaling System 7;    SS-CSI: Supplementary Service Notification CAMEL Subscription Information;    STK: Synthesis Toolkit in C++;    STP: Signaling Transfer Point;    T1: Wide Area Digital Transmission Scheme used predominantly in the United States;    TAF: Transparent Application Fail-over;    TAP: Transfer Accounting Procedure;    TADIG: Transfer Accounting Data Interchange Group;    T-BCSM: Terminating Basic Call State Model;    TCAP: Transaction Capability Part;    TCP/IP: Transmission Control Protocol/Internet Protocol;    T-CSI: Terminating CAMEL Subscription Information (in the GMSC);    TDMA: Time Division Multiple Access;    TDP: Trigger Detection Point;    TIF-CSI: Translation Information Flag;    TPDU: Transfer Protocol Data Unit;    TT: Translation Type (SS7 parlance);    U-CSI: USSD CAMEL Subscription Information;    UG-CSI: USSD General CAMEL Service Information;    Um: Interface between the mobile station (MS) and the A/Gb mode network;    UNI: User Network Interface;    USSD: Unstructured Supplementary Service Data;    Uu: Interface between the mobile station (MS) and the Iu mode network;    VHE: Virtual Home Environment;    VLR: Visited Location Register;    VLR-H: Serving VLR in HPMN;    VLR-F: Serving VLR in FPMN;    VLR-V: Serving VLR in VPMN (VPMN is not HPMN/FPMN);    VPLMN: Visited PLMN;    VPMN: Visited Public Mobile Network (other than HPMN or FPMN);    VMSC: Visited Mobile Switching Center;    VMSC-H: Serving VMSC in HPMN;    VMSC-F: Serving VMSC in FPMN;    VMSC-V: Serving VMSC in VPMN (VPMN is not HPMN/FPMN);    VT: Mobile Terminating in VMSC;    VT-CSI: VMSC Terminating CAMEL Subscription Information;    WAN: Wide Area Network;    WAP: Wireless Application Protocol; and    WiFi: Wireless Fidelity.